At the present, the type of AC-driven PDPs which are generally commercialized is the type of surface discharge PDP. In the type of surface discharge PDP, phosphor layers for color display can be positioned far away in the direction of the thickness of a display panel from a pair of display electrodes, so that the characteristic deterioration of the phosphors due to ion impact during discharging can be reduced. Thus, the type of surface discharge PDP is suitable for prolonging its life time rather than another type of opposed discharge PDP where a pair of display electrodes X and Y is formed to a front-side substrate and a rear-side substrate, respectively.
On a front-side substrate in the general type of AC-driven surface discharge PDP, a protective layer is provided for preventing a dielectric layer from being deteriorated by ion impact during discharging, the dielectric layer covering display electrodes X and Y. The protective layer not only prevents the dielectric layer from being deteriorated by ion impact during discharging, but also emits secondary electrons by ion impact thereto and provides a function to make discharge grow.
In general, the protective layer is employed as a thin film of magnesium oxide (MgO) considering high protection from ion impact and good emission capability of secondary electrons.